Management of multiple devices within an analyte monitoring environment

ABSTRACT

Systems, devices, and methods are provided for the management of multiple sensor control devices and/or multiple reader devices in an in vivo analyte monitoring environment, and also for resolving conflicts when merging data collected by different reader devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/482,955, filed Sep. 23, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/455,481, filed Jun. 27, 2019, now U.S. Pat. No.11,159,621, which is a continuation of U.S. patent application Ser. No.15/640,076, filed Jun. 30, 2017, now abandoned, which is a continuationof U.S. patent application Ser. No. 14/717,749, filed May 20, 2015, nowU.S. Pat. No. 9,723,082, which claims the benefit of and priority toU.S. Provisional Application No. 62/001,343, filed May 21, 2014, all ofwhich are incorporated by reference herein in their entireties and forall purposes.

FIELD

The subject matter described herein relates generally to the managementof multiple devices within an analyte monitoring environment.

BACKGROUND

The detection and/or monitoring of analyte levels, such as glucose,ketones, lactate, oxygen, hemoglobin A1C, or the like, can be vitallyimportant to the health of an individual having diabetes. Diabeticsgenerally monitor their glucose levels to ensure that they are beingmaintained within a clinically safe range, and may also use thisinformation to determine if and/or when insulin is needed to reduceglucose levels in their bodies or when additional glucose is needed toraise the level of glucose in their bodies.

Growing clinical data demonstrates a strong correlation between thefrequency of glucose monitoring and glycemic control. Despite suchcorrelation, many individuals diagnosed with a diabetic condition do notmonitor their glucose levels as frequently as they should due to acombination of factors including convenience, testing discretion, painassociated with glucose testing, and cost. For these and other reasons,needs exist for improved analyte monitoring systems, devices, andmethods.

SUMMARY

A number of systems have been developed for the automatic monitoring ofthe analyte(s), like glucose, in a bodily fluid of a user, such as inthe blood, interstitial fluid (“ISF”), dermal fluid, or in otherbiological fluid. Some of these systems include a sensor that can be atleast partially positioned “in vivo” within the user, e.g.,transcutaneously, subcutaneously, or dermally, to make contact with theuser's bodily fluid and sense the analyte levels contained therein.These systems are thus referred to as in vivo analyte monitoringsystems.

The sensor is generally part of a sensor control device that resides on(or in) the body of the user and contains the electronics and powersupply that enable and control the analyte sensing. The sensor controldevice, and variations thereof, can be referred to as a “sensor controlunit,” an “on-body electronics” device or unit, an “on-body” device orunit, or a “sensor data communication” device or unit, to name a few.

The analyte data sensed with the sensor control device can becommunicated to a separate device that can process and/or display thatsensed analyte data to the user in any number of forms. This device, andvariations thereof, can be referred to as a “reader device” (or simply a“reader”), “handheld electronics” (or a handheld), a “portable dataprocessing” device or unit, a “data receiver,” a “receiver” device orunit (or simply a receiver), or a “remote” device or unit, to name afew.

In vivo analyte monitoring systems can be broadly classified based onthe manner in which data is communicated between the reader device andthe sensor control device. One type of in vivo system is a “ContinuousAnalyte Monitoring” system (or “Continuous Glucose Monitoring” system),where data can be broadcast from the sensor control device to the readerdevice continuously without prompting, e.g., in an automatic fashionaccording to a broadcast schedule. Another type of in vivo system is a“Flash Analyte Monitoring” system (or “Flash Glucose Monitoring” systemor simply “Flash” system), where data can be transferred from the sensorcontrol device in response to a scan or request for data by the readerdevice, such as with a Near Field Communication (NFC) or Radio FrequencyIdentification (RFID) protocol.

Example embodiments of systems, devices, and methods are described thatallow management of multiple sensor control devices and/or readerdevices within an analyte monitoring environment. Some of these exampleembodiments involve the management of multiple reader devices in thecollection of analyte data from a single sensor control device, whileother example embodiments involve the management of analyte datacollected by a single reader device from multiple sensor controldevices, where the multiple sensor control devices belong to one user ormultiple users. These and other example embodiments can be applied to awide variety of situations involving complex interplay between devicesand users, such as situations where multiple users are present, eachhaving one or more sensor control devices, and where one or more readerdevices are used to collect the analyte data from any or all of thesesensor control devices. Also described are example embodiments that arecapable of resolving conflicts between analyte data collected onmultiple sensor control devices for a single user. Also described hereinare example embodiments of managing issues involving the estimating oftimes, resolving conflicts in times, and determining that time eventshave occurred. Although not limited to such, the embodiments describedherein are particularly suited to environments where the reader deviceis a smartphone.

Other systems, devices, methods, features and advantages of the subjectmatter described herein will be or will become apparent to one withskill in the art upon examination of the following figures and detaileddescription. It is intended that all such additional systems, devices,methods, features and advantages be included within this description, bewithin the scope of the subject matter described herein, and beprotected by the accompanying claims. In no way should the features ofthe example embodiments be construed as limiting the appended claims,absent express recitation of those features in the claims.

BRIEF DESCRIPTION OF THE FIGURES

The details of the subject matter set forth herein, both as to itsstructure and operation, may be apparent by study of the accompanyingfigures, in which like reference numerals refer to like parts. Thecomponents in the figures are not necessarily to scale, emphasis insteadbeing placed upon illustrating the principles of the subject matter.Moreover, all illustrations are intended to convey concepts, whererelative sizes, shapes and other detailed attributes may be illustratedschematically rather than literally or precisely.

FIG. 1A is an illustrative diagram depicting an example embodiment of anin vivo analyte monitoring system having a sensor control devicecommunicating with multiple reader devices.

FIG. 1B is an illustrative diagram depicting an example embodiment of anin vivo analyte monitoring system having multiple sensor control devicescommunicating with a single reader device.

FIG. 1C is an illustrative diagram depicting an example embodiment of anin vivo analyte monitoring system having multiple sensor control devicescommunicating with multiple reader devices.

FIG. 1D is a table describing capabilities for example embodiments ofreader devices.

FIG. 2 is a flow diagram depicting an example embodiment of a method ofjoining a reader device with a sensor control device that has alreadybeen activated.

FIG. 3 is a flow diagram depicting an example embodiment of a method ofusing a reader device to collect analyte data from multiple users whereeach user's data is associated with a user identifier.

FIG. 4A depicts an example embodiment of a in vivo analyte monitoringsystem where a first reader device is used to activate a sensor controldevice on the body of a user.

FIG. 4B depicts an example situation where differences occur betweentime stamps of a first reader device and time stamps of a second readerdevice corresponding to a sequence of sensor samples.

FIG. 5A is an example of an analyte data versus time graph having a timechange icon thereon.

FIG. 5B is a flow chart depicting an example embodiment of a method ofdetermining whether a time change occurred in a reader device.

FIG. 6A is a high level diagram depicting an example embodiment of ananalyte monitoring system for real time analyte (e.g., glucose)measurement, data acquisition and/or processing.

FIG. 6B is a block diagram depicting an example embodiment of a readerdevice configured as a smartphone.

FIG. 6C is a block diagram depicting an example embodiment of a sensorcontrol device.

DETAILED DESCRIPTION

The present subject matter is not limited to the particular embodimentsdescribed, as such are only examples and may, of course, vary. Likewise,the terminology used herein is for the purpose of describing particularembodiments only, and is not intended to be limiting, since the scope ofthe present disclosure will be limited only by the appended claims.

The subject matter of this description pertains generally to themanagement of multiple sensor control devices and/or multiple readerdevices within an analyte monitoring environment. In typical in vivomonitoring systems, each sensor control device is only allowed tointerface with one reader device in order to restrict access to theuser's data. That reader device is typically a dedicated-use device,i.e., one that was designed for the primary purpose of interfacing witha sensor control device, typically one built by the same manufacturer asthat of the sensor control device. However, a reader device can also bein the form of a general purpose mobile communication device, such as asmartphone. The proliferation of smartphones makes it desirable for eachuser to have the option of using his or her smartphone to interface withthe sensor control device in addition to, or instead of, a dedicated-usereader device.

The user's medical data is of a private nature and should be safeguardedfrom eavesdroppers, sometimes referred to as “snoopers.” The identity ofany reader device used to collect data from a sensor control deviceshould therefore be verified prior to sending data to that readerdevice. Example embodiments described herein provide a manner by which asensor control device can securely interface with multiple readerdevices. Such a situation is depicted with respect to the in vivoanalyte monitoring system 100 of FIG. 1A, where a user 130 uses a firstreader device 120-1 and a second reader device 120-2 to wirelesslyinterface with a sensor control device 102 monitoring that user'sanalyte levels.

Sensor control devices 102 typically have a limited operating life andit is desirable for each reader device 120 to know when that operatinglife expires so as not to collect analyte data post-expiration. However,if reader device 120-2, for example, was not the same one used toactivate sensor control device 102, then reader device 120-2 may nothave data indicating how much of sensor control device 102's operatinglife has passed. Example embodiments described herein also provide for amanner of estimating (or learning) the remaining operating life of asensor control device 102.

It is also desirable to have a reader device 120 that can interface withmultiple sensor control devices 102. Because of their limited operatinglife, typically much less than that of reader device 120, each sensorcontrol device 102 must periodically be replaced by the user, whichtypically entails removing the expired sensor control device 102 fromthe user's body and replacing it with a newly activated sensor controldevice 102. For example, replacement may occur numerous times over thecourse of a year. In some cases, a user wearing a first sensor controldevice 102 may wish to activate a second sensor control device 102 priorto the expiration of the first so as not to lose any data during thesecond sensor control device's “warm-up” period (discussed in moredetail herein). Accordingly, embodiments of reader devices 120 that caninterface with multiple sensor control devices 102 in an overlap fashionare described herein. FIG. 1B depicts an example of system 100 whereuser 130 is wearing two activated sensor control devices 102-1 and102-2, and uses a single reader device 120 to wirelessly interface withboth in an overlapped, concurrent fashion (e.g., simultaneously or in aback-and-forth manner).

Still more complex environments are contemplated herein. FIG. 1C depictsan example of one such environment having a system 100 with fourdifferent sensor control devices 102-1 through 102-4, each being worn bya different user 130-1 through 130-4, respectively, and wirelesslyinterfacing with one or more reader devices 120-1 through 120-6. FIG. 1Ddepicts a table describing the types of reader devices 120-1 through120-6 and summarizes their capabilities for comparison. Unless notedotherwise, the reader devices 120 described with respect to all of theembodiments herein can each be implemented in any of the reader deviceoperating configurations described with respect to FIG. 1C and/or FIG.1D.

In FIG. 1C, reader devices 120-1 and 120-4 are dedicated-use deviceswhere each receives analyte data from only a single sensor controldevice 102 while that sensor control device 102 is active. This isindicated by “One” in the “Users” column and the “Sensor ControlDevices” column of FIG. 1D.

Reader devices 102-1 and 120-4 can start-up or activate a sensor controldevice 102, as indicated by “Yes” in the “Activation Capability” columnof FIG. 1D. In order to receive analyte data from sensor control device102, reader devices 120-1 and 120-4 must first pair with the sensorcontrol device 102 as indicated by the “Yes” in the “Pair Required?”column of FIG. 1D. Here reader device 120-1 activates and then pairswith sensor control device 102-1 and reader device 120-4 activates andthen pairs with sensor control device 102-3 (see FIG. 1C). To pair, areader device 120 will, for example, obtain an identifier (e.g., aserial number) from the sensor control device 102 and store it withinits memory such that it can recognize that sensor control device 102during later communications (where sensor control device 102 will againsend its identifier). This can ensure that reader device 120 will onlycommunicate with a single sensor control device 102 until the useractivates and pairs with a second sensor control device 102 (which willthen replace the first).

Reader devices 120-1 and 120-4 are programmed to collect and displayrecent analyte data for each user (see the “Yes” in the “Recent”“History” column of FIG. 1D), but not to collect and display fullhistorical analyte data for each user (see the “No” in the adjacent“Full” “History” column). Recent history can be a history over theprevious day, previous 12 hours, previous 8 hours, etc. Reader devices120-1 and 120-4 are restricted from overlapping communication with asecond sensor control device 102 in an initialization period, which isdescribed in more detail below (see the “No” in the “Overlap” column).Reader devices 120-1 and 120-4 are also restricted from joining intocommunication with a sensor control device 102 that has been activatedby another reader device 120 (see the “No” in the “Confirmed Join”column).

The remaining description will focus on those aspects and capabilitiesof other reader devices 120 that differ from the configuration examplejust described.

Reader devices 120-3 and 120-5 are not dedicated-use devices but rathersmartphones each having a single-user software implementation thatallows communication with only those sensor control devices 102associated with a single user (as noted in the “Users” column of FIG.1D). In FIG. 1C, reader device 120-3 communicates with sensor controldevice 102-2 of user 130-2, and reader device 120-5 communicates withsensor control device 102-3 of user 130-3. However, these reader devices120-3 and 120-5 are programmed to allow the activation of a new sensorcontrol device 102 for the same user 130 and still maintaincommunication with the older sensor control device 102 in a limitedcircumstance, for example, while the new sensor control device 102 is inan initialization period (see the description of overlappingcommunication herein). This is shown in FIG. 1D as operation beingallowed with “Multiple” sensor control devices due to the allowed“Overlap” capability.

As shown in FIG. 1C, reader device 120-5 can join communications (e.g.,by pairing) with a sensor control device 102-3 that has already beenactivated by a different reader device 120-4, so long as that sensorcontrol device 102-3 belongs to the same user 130-3 as all of the othersensor control devices 102 with which reader device 120-5 is paired.Upon joining communication, reader device 120-5 can only communicatewith that sensor control device 102-3 (as indicated by “One” in thesensor control device column of FIG. 1D). The same capability is presentfor reader device 120-3.

Moving to the next example, reader device 120-2 is not a dedicated-usedevice but rather a smartphone intended for use by, for example, aparent of multiple children each requiring analyte monitoring.Smartphone 120-2 has a multi-user software implementation that allowscommunication with sensor control devices 102-1 and 102-2 belonging todifferent child wearers 130-1 and 130-2, respectively. Thesecapabilities are indicated by “Multiple” in the “Users” and “SensorControl Devices” column of FIG. 1D. In this example, the remainingcapabilities of FIG. 1D are the same as for reader devices 120-3 and120-5.

Reader device 120-6 is an example of a reader device configured for aclinical setting where the operator is a medical professional. Readerdevice 120-6 can be any type (e.g., dedicated-use, smartphone, etc.) andcan be configured to operate in a number of different modes depending onthe particular situation.

The first mode is applicable to situations where infrequent in-personcontact occurs with user/wearer 130 (e.g., once per week, once per twoweeks, once per month, etc.). In these situations, the health careprovider is primarily interested in the current analyte level of user130. A number of these types of settings exist. For example, a physicaltherapy provider may see multiple patients (in-person) infrequently andwant to evaluate their analyte levels prior to commencing therapy. Thefirst mode is particularly applicable to sensor control devices 102 thathave not yet expired (i.e., pre-expiration). In this first mode, readerdevice 120-6 can activate and interface with any number of sensorcontrol devices 102 belonging to any number of users 130, and is notrequired to pair with those sensor control devices 102 in order tocalculate and display the current analyte level for each user 130.Without pairing, reader device 120-6 is generally not able to associatesensor control devices 102 with a particular user, so reader device120-6 does not log the recent history or the full history.

The second mode is applicable to situations where there is frequentin-person contact with user 130 (e.g., periodically throughout the day).A number of these types of settings exist, for example, in the case of ahome care provider. This mode is similar to the example for readerdevice 120-2 used with a parent of multiple children. This mode isparticularly suitable for sensor control devices 102 that have not yetexpired. In this mode, reader device 120-6 can activate and interfacewith any number of sensor control devices 102 belonging to any number ofusers 130. In this example, reader device 120-6 must pair to associate auser with sensor control device 102. Reader device 102-6 logs the recenthistory so that it can be reviewed for each user 130. Downloading thefull historical data is not permitted as it can be a lengthy processthat drains the power source of sensor control device 102, especially ifreader device 120-6 is downloading the entire history at one time.

The third mode is applicable to scheduled in-person contact with user130 (e.g., commonly infrequently, but also frequently). The health careprovider is interested in the current analyte level, as well as in thehistoric analyte levels. A number of these types of settings exist, forexample a primary physician or a health and wellness coach. This mode isparticularly suitable for sensor control devices 102 that have not yetexpired. In this mode, reader device 120-6 can activate and interfacewith any number of sensor control devices 102 belonging to any number ofusers 130. Reader device 120-6 pairs to associate a user 130 with sensorcontrol device 102. Reader device 120-6 logs the recent history so thatit can be reviewed for each user 130. Reader device 120-6 also downloadsthe full historical data to have as much historic information aspossible when evaluating and counseling the user 130.

The fourth mode requires no in-person contact with user 130. Since theuser 130 is not present, the health care provider is only interested inthe historic analyte levels. A number of these types of settings exist,for example a return mail service. Sensor control device 102 will havenormally expired when this mode is used. There is also no need toactivate nor pair with sensor control devices 102 in this mode and thusthose functions are not present. There is also no need for the recenthistory because it is duplicated in the full history. Reader device120-6 does download the full history.

The sensor control device capability drives some of the modedifferentiators. For example, a low cost sensor control device 102 maynot have full history capability. A reader device 120 may include morethan one mode depending on the type of sensor control device 102. Forexample, a reader device 120 can employ the second mode with a low costsensor control device 102, and can employ the third mode with a fullhistory capable sensor control device 102.

As mentioned above, certain smartphone reader devices 120 can join witha sensor control device 102 that has already been activated by adifferent reader device 120. See FIG. 1C, for example, where smartphonereader device 120-2 joins into communication with sensor control device102-1 after it has already been activated by dedicated-use reader device120-1.

FIG. 2 is a flow diagram depicting an example embodiment of a method 200of joining a reader device 120 with a sensor control device 102 that hasalready been activated. Although not limited to such, in this examplethe joining reader device 120 is a smartphone. At 262, the joiningsmartphone 120 is provided with an access token that can be used bysensor control device 102 to verify that smartphone 120 is an authorizedreader device, e.g., a reader device 120 associated with the wearer ofsensor control device 102. The access token can be any string ofcharacters that is suitable for use as a passcode. The access token canbe random or pseudorandom and can be comprised of letters, numbers,and/or symbols. The access token can be provided by the sensor controldevice manufacturer or can be set by the user.

If the access token is set by the user, it is desirable to accomplishthis when the sensor control device 102 is originally activated forsecurity purposes. Upon powering up sensor control device 102, the userwould enter the string of characters chosen (to act as the access token)into the activating reader device 120 (e.g., using any of the reader'suser interface features). That chosen access token can then be hashed,stored within smartphone 120, and sent to sensor control device 102,which can store the token to an onboard writable memory (e.g., memory253 described with respect to FIG. 6C). Any further communications fromthe activating reader device 120, such as a request for measured analytedata (sometimes referred to as a “scan”), can include the hashed accesstoken. Upon receipt, sensor control device 102 can compare the receivedaccess token to the one stored in memory and, if the two access tokensmatch, sensor control device 102 can respond appropriately, such as bysending the user's measured analyte data or any other requestedconfidential data, to the activating reader device 120.

Since the user knows the selected access token, the user can then enterthe selected access token at step 262 into a second reader device 120that is joining communication with the already activated sensor controldevice 102.

If the access token is provided by the manufacturer (or a similarentity), then it is desirable for the access token to be stored withinany writable or read-only memory of sensor control device 102 at thetime of manufacture.

That same access token is then also to be provided to smartphone 120 at262, in any of a number of ways. For example, the packaging for acomponent of in vivo analyte monitoring system 100 can have the accesstoken printed thereon. The access token can be printed in human-readableform, e.g., on a holographic label, such that the user can input theaccess token directly into smartphone 120 in step 262. This may, forexample, be in response to a prompt by a user interface applicationoperating on smartphone 120.

The access token can also be printed in machine-readable form, such asin the form of a barcode. The barcode can be a one-dimensional barcode,two-dimensional barcode, or three-dimensional barcode and can be of anyformat (QR code, data matrix, maxicode, aztec code, QR code, etc.).Printed indicia other than barcodes can be used as well. In such anexample, an optical scanner (e.g., a camera) of the reader device canoptically scan the barcode to provide the access token to the readerdevice in step 262.

In another example, the access token is stored in an RFID (or NFC) labelor tag accompanying the packaging and can be read using an RFID (or NFC)scanner that is part of smartphone 120. Other machine-readable formatscan be used to obtain the access token from the packaging. The packagingitself can be a container for any part of system 100 that is supplied tothe user. For example, the packaging can be a container for sensorcontrol device 102 alone, a container for multiple sensor controldevices 102 (e.g., a multi-pack), a container for sensor control device102 in combination with an inserter 150 (see FIG. 6A herein), acontainer for inserter 150 alone. The “packaging” can also refer toinserts, labels, instructions, manuals, or the like that are containedwithin or otherwise shipped with system 100.

In yet another example, the access token can be stored in the memory ofthe activating reader device 120 and either displayed to the user (suchthat the user can then manually enter the access token into the joiningsmartphone 120), or electronically communicated to the joiningsmartphone 120, with a wired connection (e.g., USB) or wirelessconnection (e.g., Bluetooth, Bluetooth Low Energy, NFC, RFID, or aninternet or other high bandwidth connection).

In all of these embodiments, the provision of the access token tosmartphone 120 can be done at a time of the user's choosing or inresponse to a prompt to do so by reader device 120.

Referring back to FIG. 2 , the joining smartphone 120, now havingreceived the access token at 262, can send a request to sensor controldevice 102 to join into communication with that device 102 at 264. Thisrequest may be purpose-specific, i.e., one generated for the primarypurpose of joining with sensor control device 102, or the request may bea standard data request (such as a request for measured analyte data)that is interpreted by sensor control device 102 as not only a requestfor the data but also a request to join into communication. The requestcan include the hashed access token. Upon receipt of the request, at 266sensor control device 102 can compare the access token stored in memoryto the received access token to determine if it is valid. At 268, if thetwo access tokens match, sensor control device 102 can confirm tosmartphone 120 that it has been allowed to join, or can send the user'smeasured analyte data or any other requested confidential data tosmartphone 120, or otherwise. If the two tokens do not match, then at270 sensor control device 102 can send a notification of such to readerdevice 120 and refuse to respond with the requested data.

In some embodiments, each communication sent by a reader device 120 to asensor control device 102 will not only include the access token butalso a unique identifier of that reader device 120. Sensor controldevice 102 can maintain a list of approved reader devices 120 and canalso be programmed to allow communications with only a limited number ofreader devices 120 at any time, e.g., as a safeguard against multiplesurreptitious joins should the access token become public. In otherembodiments, sensor control device 102 will respond to any request fordata from a reader device 120 so long as that request contains thecorrect access token, regardless of the identity of the requestingdevice 120 and regardless of the number of devices 120 with which sensorcontrol device 102 has already transmitted confidential data to.

The operating life of a sensor control device 102 is typically basedupon a maximum duration of time over which sensor 104 can reside withinthe user's body and continue to provide accurate measurements. In someembodiments, sensor control device 102 will have an end of life count(C_(MAX)) stored in memory. Sensor control device 102 can regularlyincrement an on-board counter during its life and terminate itsoperation once the counter reaches the C_(MAX) limit. The C_(MAX) limitcan assume worst case clock error and temperature drift scenarios toensure that sensor control device 102 does not operate past the intendedoperation life. If the activating reader device 120 has a reliable clockand records the activation time of sensor control device 102, then insome embodiments the clock of reader device 120 can be used to monitorthe length of time at which sensor control device 102 has been activeand cause termination of sensor control device 102 when the full lifehas been reached. If no reader device 120 causes termination, thensensor control device 102 will do so itself once it reaches C_(MAX).

Reader devices 120 may be permitted to join communication with sensorcontrol device 102 at any time during the life of sensor control device102. In certain embodiments though, reader devices 120 may only bepermitted to join communication with a sensor control device 102 duringa predetermined time period after sensor control device 102 is initiallyactivated (e.g., a time significantly shorter than the operating life).The time at which initial activation occurs is the “activation time” andgenerally refers to the time that the sensor control device 102 ispowered on (or exits any low power or sleep state) and beginsinitialization for measuring analyte data of the wearer. Permittingjoining within this predetermined time period increases the likelihoodthat the pairing is authorized and protects against “snooping.” Use ofthe predetermined time period can also ensure that the joining readerdevice 120 is paired early in the operating life of the sensor controldevice 102 so that the joining reader device 120 will have a moreaccurate estimate of the activation time of device 102 (e.g., typicallyonly the activating reader device 120 knows the actual activation time).As mentioned, reader device 120 may be programmed so as not to requestor accept analyte data from a sensor control device 102 after thatdevice 102 has exceeded its operating life.

In some of these embodiments, the predetermined time period is the sameas an initialization time period, sometimes referred to as a “warm-up”period, for sensor control device 102. The initialization period canallow the chemistry of sensor 140 to reach equilibrium and stabilizeafter activation. The display of real-time glucose values is delayeduntil after this initial period of instability.

The initialization time period is less than the operating life of device102, and in many embodiments is substantially less than the operatinglife. The predetermined time period can be 15% of the operating life,10% of the operating life, 5% of the operating life, or 1% of theoperating life, to name a few examples. In one example, sensor controldevice 102 has an operating life of 14 days and the predetermined timeperiod is one (1) hour.

Reader device 120 can include software programming for estimating theactivation time of sensor control device 102. An example of a formula(1) for this estimation is below.

$\begin{matrix}{T_{EST} = {T_{CUR} - \left\lbrack {C*I*\left( {L_{FC}/L_{STD}} \right)*D} \right\rbrack}} & (1)\end{matrix}$

Here, T_(EST) is the estimated activation time of sensor control device102 and T_(CUR) is the current time of reader device 120. C is thecurrent count of sensor control device 102, which can be the value of asequential counter that is updated after the passage of a count timeinterval (I). Interval (I) can be a fixed or set time interval betweencounter increments, or can be realized using a regularly repeating, orpseudo-regularly repeating data collection interval that occurs withinsensor control device 102. Other approaches can be used as well.

But in many embodiments the clock may have a lower accuracy and maydrift, such as due to temperature. In these cases, the count intervalfor each sensor control device 102 can be measured by the manufacturerto arrive at a device-specific correction value (L_(FC)), e.g., ameasured clock frequency of the particular sensor control device 102.The clock offset can be corrected using the correction value along withan ideal value (L_(STD)) for that class or model of sensor controldevice 102, e.g., the standard clock frequency.

D is a factor that corresponds to the maximum (or worst-case) drift ofthe clock of sensor control device 102. In an ideal situation, sensorcontrol device 102 would remain at the same temperature as when L_(FC)was calculated. But if, for example, the temperature was higher thanwhen L_(FC) was calculated, then the oscillator will have run slow and Cwill under-represent the actual number of minutes that have transpired.D is determined by the sensor control device clock characteristics andwill typically be a little greater than one (1.00) to ensure that thetime since activation is not underestimated. In some embodiments,real-time temperature readings can be taken and relied upon to scale(reduce or increase) D to more accurately reflect the conditionsexperienced by sensor control device 102, and thus produce a moreaccurate estimation.

In certain embodiments, C is incremented approximately every one minuteas determined by a clock (e.g., a crystal oscillator or an RCoscillator) of sensor control device 102. In embodiments where the clockaccuracy is very good and is minimally subject to variation, T_(EST) isT_(CUR) minus the number of sensor counts (C) times the count interval(I) (e.g., one minute, two minutes, etc.).

After joining, sensor control device 102 will communicate theaforementioned information (e.g., C, L_(FC), L_(STD)) required by readerdevice 120 to perform the activation time estimate. This time estimate(or an estimated duration of time that has passed since activation) canthen be used to determine the remaining operating life for sensorcontrol device 102. If the sensor control device clock is perfect andthe temperature remains constant, then equation (1) is simplified toequation (2) below.

$\begin{matrix}{T_{EST} = {T_{CUR} - \left\lbrack {C*I} \right\rbrack}} & (2)\end{matrix}$

If reader device 120 scans sensor control device 102 after the end ofthe full life but before C_(MAX), then reader device 120 will only usethe analyte data up to the end of the operating life as determined bythe real activation time or the earlier estimated activation time.

The use of equation (1) to estimate the remaining operating life for thesensor control device 102 can incorporate the worst case scenario forclock drift (as described above), in which case the estimatedtermination will likely be premature, or early, assuming that the sensorcontrol device 102 does not actually experience worst case conditions.In certain embodiments, the maximum error (T_(EST)-T_(ACT)) is estimatedby formula (3) below.

$\begin{matrix}{{MaximumError} = {{T_{EST} - T_{ACT}} = {S*\left( {L_{FC}/L_{STD}} \right)*\left( {D - 1} \right)}}} & (3)\end{matrix}$

Table 2 shoes error values based on a 14 day operating life. The valuesin Table 2 are maximum values, and in practice will typically be abouthalf (or less) of these maximums. As can be seen here, the longer intothe operating life one waits to join reader device 120 with sensorcontrol device 102, the greater the maximum error will be, and theshorter the operating life will become if one wishes to safeguardagainst inadvertently using device 102 after its expiration.Nevertheless, even if reader device 120 joins 14 days into the operationof sensor control device 102, the premature termination of device isonly about 155.7 minutes, or less than three hours.

TABLE 2 Age (days) of Sensor Early Expiration Control Device 102 SampleNumber (minutes) 0 0 0.0 1 1440 11.1 2 2880 22.2 3 4320 33.4 4 5760 44.55 7200 55.6 6 8640 66.7 7 10080 77.8 8 11520 89 9 12960 100.1 10 14400111.2 11 15840 122.4 12 17280 133.5 13 18720 144.6 14 20160 155.7

As an alternative to estimation using equation (1), the activatingreader device 120 can communicate the actual activation time (or currentduration of operation) to the non-activating reader device 120 over awireless or wired data communication link.

Referring back to the initialization time period, as mentioned it may bedesirable for a user to continue to collect data from an older sensorcontrol device 102 while initializing a newer sensor control device 102.This will allow the user to continue to monitor his or her analyte levelwith the older sensor control device 102 while the newer sensor controldevice 102 transitions through the initialization time period (e.g.,“warms up”). In those cases, the reader device 120 that was used toactivate the older sensor control device 102 may also be used toactivate the newer sensor control device 102 and may need to “overlap”communication with both devices 102 (similar to the situation of FIG.1B).

In some embodiments, the software of reader device 120 will treat theolder sensor control device 102 as the primary sensor control device.The primary sensor control device will be presented to the user on thereader device display as the “active” control device 102 or the sensorcontrol device 102 that is currently being relied upon to provideanalyte data to the user. The reader device 120 can select the newersensor control device 102 as the primary sensor control device oncereader device 120 receives data indicative of the current analyte levelof the user after exiting the initialization period. For example, thefirst time that the user scans the newer sensor control device 102 afterthat sensor control device 102 has exited the initialization or warm-upperiod, the reader device 120 will select the newer sensor controldevice 102 as the primary sensor control device and display it as suchto the user.

Analyte data collected from the older sensor control device 102 can bedistinguished from analyte data collected from the newer sensor controldevice 102 based on an identifier that is unique to each sensor controldevice 102 and communicated with that sensor control device's analytedata. The identifier, referred to herein as a sensor ID, can be anystring of characters (e.g., numbers, letters, or symbols) that uniquelyidentifies the associated sensor control device 102 within system 100.While the sensor ID can be unique in an absolute sense, it is sufficientfor the sensor ID to be substantially unique among the set of sensorcontrol devices 102 that may be used with the user's reader devices 120.

In many embodiments it is desirable for a reader device 120 to collectanalyte data from multiple users, for example, a care providermonitoring analyte levels for the elderly or a parent monitoring analytelevels for several children. In these embodiments, the data collected bythe reader device operator for each user is associated to that user witha user identifier, or user ID. The user identifier can be any string ofcharacters that uniquely identifies the user. The user identifier can benon-random, random or pseudorandom and can be comprised of letters,numbers, and/or symbols. As with the sensor ID, the user identifier canbe unique in an absolute sense, it is sufficient for the sensor ID to besubstantially unique among the set of sensor control devices 102 thatmay be used with the user's reader devices 120.

FIG. 3 is a flow diagram depicting an example embodiment of a method 300of using a reader device 120 to collect analyte data from multiple userswhere each user's data is associated with a user identifier. In thisexample, reader device 120 is a smartphone. At 302, smartphone 120initiates communication with sensor control device 102. This can be arequest to pair with sensor control device 102 or a request for analytedata from sensor control device 102. At 304, sensor control device 102provides its sensor ID to smartphone 120. At 306, smartphone 120requests that the user assign a user ID for any analyte data that iscollected from the sensor control device 102. This would be accomplishedwith a prompt displayed to the user on a display 122 (see FIG. 6A) ofsmartphone 120, but could also be performed at the initiative of theuser. At 308, the software of smartphone 120 determines whether the userhas entered a user ID for the sensor control device 102 and, if so, thensmartphone 120 proceeds to store any collected analyte data from sensorcontrol device 102, e.g., based on the sensor ID, in a manner thatassociates it with the user ID at 310.

If the user fails to enter a user ID, then, at 312, a warning can bedisplayed on the smartphone 120 that normal processing of the analytedata will not occur and smartphone 120 will take that correspondingaction. This can include refusing to display the current analyte data tothe user, refusing to save the analyte data on smartphone 120 (whichalso would prevent the display of historical analyte data), bothaforementioned actions, or other actions.

At 314, smartphone 120 can collect additional analyte data from thissensor control device 102, or from a second sensor control device 102.If smartphone 120 does not have a user ID associated with that secondsensor control device 102, then, after initiating communication with thesecond sensor control device 102, smartphone 120 can repeat steps 304through 308 as needed for that second sensor control device 102, withoutcomes 310 or 312. This process can be repeated for any number ofsubsequent sensor control devices 102.

In cases where a reader 120 communicates with and collects analyte datafrom multiple sensor control devices 102, the smartphone software hasthe capability to retrieve a list of all active and inactive sensorcontrol devices with each one's associated activation times, expirationtimes, and times at which the sensor control device exits theinitialization period. In some embodiments, an API can execute a search(e.g., SQL) that returns the results in a data structure (e.g., list,table, array, etc.).

In cases where a reader 120-2 collects data from a sensor control device102 activated initially by another reader 120-1, that data collectionfunctionality can be independently permitted or prevented. In otherwords, the capability of reader 120-2 to read data from the alreadyactive sensor control device can be configured by the user aspermissible or not permissible.

Each reader device 120 can have informatics software stored thereon thatallows the display of historical analyte data and that includes featuresor tools to assist in the analysis of the historical analyte data. Theinformatics software could also be installed on a remote terminal 170(described with respect to FIG. 6A below), e.g., a personal computer ora tablet, or could be hosted by a trusted network (not shown), such asan internet server or other computer system. In these examples the userwould upload the analyte data from the collecting reader device(s) 120to remote terminal 170 or a trusted server prior to acting upon thatdata with the informatics software. One example of an informaticssoftware program is the commercially available GLOOKO application.

Regardless of where the informatics software is installed, in theembodiments described herein a user can collect analyte data from asingle sensor control device 102 using multiple different reader devices120, and this can lead to conflicts when providing the data to theinformatics software. FIG. 4A depicts an example embodiment of a system100 where a first reader device 120-1 is used to activate a sensorcontrol device 102 on the body of a user 130. That reader device 120-1is used to collect analyte data from sensor control device 102. User 130also uses a second reader device 120-2 to collect analyte data fromsensor control device 102. The collected analyte data is stored onreader device 120-1 as a data compilation (or data set) 402-1 and onreader device 120-2 as a data compilation 402-2. Both data compilations402-1 and 402-2 are provided (e.g., uploaded) to informatics software404 in a manner that associates them with the sensor ID and the user'sID 403. (While it is possible to associate data compilations 402-1 and402-2 with just the sensor ID, this does not allow the user's historicaldata to be analyzed across multiple sensor control devices 102.) Theuser ID may be stored and transferred in a data file separate from theraw analyte data and sensor ID value, which may facilitate HIPAAcompliance and facilitate the creation of a map of user ID's to sensorID files by software 404.

Software 404 then merges the data compilations 402-1 and 402-2 into amerged data compilation 406, which may also include historical analytedata for the user taken from other sensor control devices 102, with allsuch data linked together with the user ID 403.

Because different reader devices 120-1 and 120-2 were used, it ispossible that one or more conflicts exist between data compilations402-1 and 402-2, which in turn can make the merger process difficult.One such conflict can result from non-synchronized clocks, i.e., thetime setting of reader device 120-1 may not match the time setting ofreader device 120-2. For example, the time setting for reader device120-1 may have been set by the user while the time setting for readerdevice 120-2 may be sourced from a telecommunications network, there maybe phase drift with the clock of one of the reader devices 120-1 and120-2, or the two reader devices 120-1 and 120-2 may be set to differenttime zones as the result of travel, and so forth. The sensor ID andsensor count (or sensor sample number) are sourced from sensor controldevice 102 itself and can be used to align or otherwise overlay the twodata compilations 402-1 and 402-2. But conflicts can arise in the timestamps accompanying the two data compilations 402-1 and 402-2 since theyare generated by reader devices 120-1 and 120-2, respectively.

FIG. 4B depicts an example situation where differences occur betweentime stamps 411 of reader device 120-1 and time stamps 412 of readerdevice 120-2 for a sequence of sensor samples 414. A first timedifference appears at sample number 422 where reader device 120-1 hasdrifted ahead of reader device 120-2 by one minute. This one minuteoffset carries through the remainder of the sample numbers that areshown, but a further difference is introduced at sample number 424 whena local time change occurs at reader device 120-2.

Conflicts may also arise in merging the data if there are differences inthe filtering or smoothing functions performed by reader devices 120-1and 120-2. In some embodiments, different reader devices 120 cancalculate and record different results for a particular raw analyte datasample recorded by a sensor control device 102. Certain filteringalgorithms executed by a reader device 120 can use other analytemeasurements occurring before and/or after the particular data sample inorder to provide additional context with which to determine what thebest analyte value is for the particular data sample.

Referring back to FIG. 4B, both reader devices 120-1 and 120-2 havecollected the raw data for sample numbers 420-425, but reader device120-1 has only collected the raw data for sample number 426 and not forsample number 427. Conversely, reader device 120-2 has only collectedthe raw data for sample number 427 and not for sample number 426. If,when determining the analyte level that corresponds to the raw data ofsample 425, each reader device 120-1 and 120-2 uses samples occurringboth before and after sample 425, then reader devices 120-1 and 120-2will be working with different data, as reader device 120-1 does nothave sample 427 and reader device 120-2 does not have sample 426. Thefiltering algorithms on each reader device 120 may interpret sample 425differently when converting to, e.g., the current analyte value orcurrent analyte rate of change.

Software 406 can reconcile these conflicts (e.g., time, filtering) in anumber of ways. In some embodiments, software 406 can request that theuser identify which reader device 120 should be used as a “master”within resolving conflicts. For example, if there is a conflict betweendata compilations 402-1 and 402-2, then the user can select eitherreader device 120-1 or reader device 120-2 to act as the master, inwhich case all conflicts will be resolved in favor of the master. Forexample, the master's time setting can be used in place of thenon-master's; the master's filtered data or smoothed data can be used inplace of the non-master's; the master's filtering algorithm or smoothingalgorithm can be used on the data of the non-master device to generatenew data; or all combinations thereof. In other embodiments, software406 can default to a particular class of reader device 120 as the masterdevice. For example, if only one smartphone reader device 120 was used,then that smartphone device will be designated the master by defaultsince it has a network synchronized clock. In alternative embodiments,software 406 can default to the activating reader device 120 as themaster device. In still other embodiments, a dedicated-use activationdevice that can synchronize with a local network clock can serve as themaster. The designation of this type of device (or a smartphone) as themaster can be most useful when the other reader device 120 is a devicethat has not been synchronized to a network clock (e.g., somededicated-use type devices).

Current time settings often vary between devices due to clock drift,changes by the user, e.g., as a result of travel between time zones,daylight savings time, correcting incorrect times, and the like. Becauseof these variances, conflicts in recorded time within an analyte datasetoften occur. While these conflicts can result from multiple readers 120taking data from a single sensor control device 102, or a single reader120 taking data from multiple sensor control devices 102, they can alsooccur when a single reader device 120 takes data from a single sensorcontrol device 102.

For example, when a smartphone reader device 120 receives dataindicative of an analyte level from sensor control device 102 (e.g.,after performing a scan), reader device 120 can timestamp that datausing the current time taken from the reader's clock, which may be thesame smartphone system clock that provides or sources the current timefor display to the user. If the user changes time zones immediatelysubsequent to a scan and the system clock is changed accordingly, thenit is possible that the next sensor scan by the smartphone reader device120 will result in data that has the same or an earlier timestamp(independent of the time zone).

Consider a user that flies from New York to Los Angeles and, during theflight, scans sensor control device 102 at 7 am, 8 am, 9 am, 10 am, 11am and 12 pm Eastern Standard Time (EST). A smartphone reader 120 thattimestamps collected analyte data without reference to the time zonewill show data collections at those times but without noting EST.Shortly after landing the time on the smartphone reader 120 is correctedto 10 am pacific standard time (PST) and the user performs a scancollecting analyte data at every hour thereafter, resulting in analytedata with timestamps of 10 am, 11 am, 12 pm, 1 pm, 2 pm, 3 pm, and soforth. The resulting analyte data will overlap and there will be twovalues for 10 am, 11 am, and 12 pm.

Display of this analyte data to the user in overlapping fashion in agraph or logbook can be confusing without some indication that a timechange occurred. FIG. 5A is a sample screen 420 that graphs analyte date(Y axis) versus time (X axis) that can be shown on display 122 of readerdevice 120 (smartphone, dedicated use, or otherwise). Here, fromapproximately 8:00 pm to 8:45 pm an overlap occurs between analyte levelcurves 422 and 424. Reader device 120 brings this to the user'sattention by display of a time change icon 426, which informs the userthat the overlap was a result in clock settings that were changed.

Automatic detection of the time change by a smartphone reader 120 can bedifficult. For one, a glucose monitoring application that runs on top ofthe smartphone's operating system (OS), e.g., Windows, Mac OSX, Android,iOS, is not directly informed when the system time is changed. Thesystem uptime is available, but it is not a true monotonic clock (i.e.,a clock that constantly moves forward and does not cease or reset) sinceit resets each time the smartphone is rebooted, turned off, runs out ofpower, etc. Furthermore, even if time changes are detected, the glucosemonitoring software must identify only those time changes that aresignificant for the purposes of data presentation with a time changeicon or other time change indicator.

Embodiments are provided herein that consult multiple clock data sourcesto reliably and automatically detect significant time change events.FIG. 5B is a flow diagram depicting a method 500 of detecting timechanges in the system clock (e.g., see clock 219 of FIG. 6B) of a reader120, which in this embodiment is a smartphone. At 501, smartphone reader120 obtains a reference time from sensor control device 102. This can bea timestamp of recently collected analyte data received from sensorcontrol device 102, or a time of activation of sensor control device, orany other time that can be used as a reference point by smartphonereader 120 to correlate the sensor control device's time to thesmartphone's time.

At 502, smartphone reader 120 receives data indicative of an analytelevel of a user from sensor control device 102 (e.g., as a result of anNFC scan). Smartphone reader 120 also receives a timestamp for theanalyte data generated by a clock of sensor control device 102 (e.g.,see clock 255 of FIG. 6C) that indicates when the analyte data wassensed or collected. If a scan is performed, then the analyte data willbe time stamped with a time that is essentially current. But if asignificant delay occurs between data collection and transmission, e.g.,5 minutes or more, then sensor control device 102 can send a currenttime value as well. As noted in the description of FIG. 6C, thistimestamp may be an actual time value or may be an integer valuereflecting the amount of time that has passed since sensor controldevice activation (e.g., the number of seconds, or the number ofminutes).

At 504, smartphone reader 120 compares the timestamp of the analyte datareceived (or the current time or other time value) from sensor controldevice 102 with the reference time obtained from sensor control device102 in step 501 to determine the difference, i.e., the sensor delta.Smartphone reader 120 also compares the time on the smartphone clockthat the analyte data was received (or current time or other time value)with the time on the smartphone clock that correlates to the referencetime obtained in step 501 to determine the difference, i.e., the readerdelta. At 505, it can be determined whether the sensor delta issufficiently large to warrant a time change analysis by comparison ofthe sensor delta to a minimum time change threshold. If the sensor deltais too small, e.g., less than 5 minutes, less than 10 minutes, less than15 minutes, and so forth, then it may not be worthwhile for the systemto perform a time change evaluation. For example, the system may have aminimum threshold that prevents the display of data taken too closetogether in time. If the sensor delta is sufficiently large, then theprocess can proceed to 506. Otherwise the process can cease.

At 506, the sensor delta and the reader delta are compared. If no timechange has occurred in the time between steps 501 and 502, then thesensor delta and reader delta will be the same and process 500 can end.If the two deltas do not match, then it is possible that a userinitiated time change occurred and the process proceeds to 508.

At 508, smartphone reader 120 will analyze whether the change can beattributed to drift or causes other than a change resulting from a useradjusting the clock. For example, a maximum drift can be determinedtaking into account the error tolerances of the two clocks (e.g., 219and 255). The clock tolerances will differ by implementation. In someembodiments, the tolerance for the clocks of the sensor control deviceand the reader device can the same or different, and can be +/−1%, 2%,3% and so forth, but may be much smaller as well.

If the difference in deltas is less than the maximum drift, thensmartphone reader 120 will not attribute the possible time change touser action but rather to drift, and cease the process. If thedifference in deltas is greater than the maximum drift, then process 500can conclude that a time change occurred and proceed to 512.Alternatively, it can be separately determined whether the sensor deltais within the maximum drift for the sensor control device's clock, andwhether the reader delta is within the maximum drift for the smartphonesclock and, if either or both are outside of the respective maximumsconclude that a time change is possible and proceed.

Process 500 can also assess whether the time change is significantenough for the application by comparing the time change to a minimumthreshold at 510. The threshold can be, for example, one or two minutes,or any other value that filters out time changes that would beinsignificant for the application. Excessive display of time changeicons even when little or no risk of overlap will be present can beundesirable.

If the time change is less than the threshold, e.g., only on the orderof one or two minutes, then process 500 can cease. If the time change isgreater than the threshold, then process 500 can conclude that a timechange occurred and, at 512, mark the dataset as having a time change orotherwise cause the display of a time change icon 426 in any analytegraphs (glucose value, rate of change, glucose trends, etc.) and/orcause the display of a similar icon or notation in any log or logbookfeature (such as a list, table, or spreadsheet). Marking the dataset mayinclude sending a notification from a sensor interface applicationresponsible for interfacing with sensor control device 102 across an APIto a user interface application responsible for generating the displaysfor the user.

As one of ordinary skill in the art will recognize after reading thisdisclosure, given the nature of process 500 steps may be performed invarious orders (e.g., step 505 can be performed at any time) and somesteps may be omitted if not desired for the actual implementation,including but not limited to steps 505, 512, and 514.

FIG. 6A is an illustrative view depicting an example embodiment of invivo analyte monitoring system 100 with which the embodiments describedthus far may be used. System 100 is depicted here with a single sensorcontrol device 102 and a single reader device 120, but multipleiterations of each may be present as in the embodiments described above.Sensor control device 102 and reader device 120 can communicate witheach other over a local communication path (or link) 140, which can bewired or wireless, and uni-directional or bi-directional. In embodimentswhere path 140 is wireless, a near field communication (NFC) protocol,RFID protocol, Bluetooth or Bluetooth Low Energy protocol, Wi-Fiprotocol, proprietary protocol, or the like can be used. Reader device120 is also capable of wired, wireless, or combined communication overcommunication paths (or links) 141 and 142 with other systems ordevices, such as a computer system 170 (e.g., a server for a website, apersonal computer, a tablet, and the like) or cloud-based storage 190.Communication paths 141 and 14 can be part of a telecommunicationsnetwork, such as the internet, a Wi-Fi network, a local area network(LAN), a wide area network (WAN), or other data network.

Variants of devices 102 and 120, as well as other components of an invivo-based analyte monitoring system that are suitable for use with thesystem, device, and method embodiments set forth herein, are describedin U.S. Patent Publ. No. 2011/0213225 (the '225 Publication), which isincorporated by reference herein in its entirety for all purposes.

Sensor control device 102 can include a housing 103 containing in vivoanalyte monitoring circuitry and a power source (shown in FIG. 2B). Thein vivo analyte monitoring circuitry is electrically coupled with ananalyte sensor 104 that extends through a patch 105 and projects awayfrom housing 103. An adhesive layer (not shown) can be positioned at thebase of patch 105 for attachment to a skin surface of the user's body.Other forms of body attachment to the body may be used, in addition toor instead of adhesive. Sensor 104 is adapted to be at least partiallyinserted into the body of the user, where it can make contact with theuser's bodily fluid and, once activated, used with the in vivo analytemonitoring circuitry to measure and collect analyte-related data of theuser. Generally, sensor control device 102 and its components can beapplied to the body with a mechanical applicator 150 in one or moresteps, as described in the incorporated '225 Publication, or in anyother desired manner.

After activation, sensor control device 102 can wirelessly communicatethe collected analyte data (such as, for example, data corresponding tomonitored analyte level and/or monitored temperature data, and/or storedhistorical analyte related data) to reader device 120 where, in certainembodiments, it can be algorithmically processed into datarepresentative of the analyte level of the user and then displayed tothe user and/or otherwise incorporated into a diabetes monitoringregime.

As shown in FIG. 6A, reader device 120 includes a display 122 to outputinformation to the user and/or to accept an input from the user (e.g.,if configured as a touch screen), and one optional user interfacecomponent 121 (or more), such as a button, actuator, touch sensitiveswitch, capacitive switch, pressure sensitive switch, jog wheel or thelike. Reader device 120 can also include one or more data communicationports 123 for wired data communication with external devices such ascomputer system 170 (described below). Reader device 120 may alsoinclude an integrated or attachable in vitro meter, including an invitro test strip port (not shown) to receive an in vitro analyte teststrip for performing in vitro blood analyte measurements.

Computer system 170 can be used by the user or a medical professional todisplay and/or analyze the collected analyte data with an informaticssoftware program. Computer system 170 may be a personal computer, aserver terminal, a laptop computer, a tablet, or other suitable dataprocessing device, and can be (or include) software for data managementand analysis and communication with the components in analyte monitoringsystem 100.

The processing of data and the execution of software within system 100can be performed by one or more processors of reader device 120,computer system 170, and/or sensor control device 102. For example, rawdata measured by sensor 104 can be algorithmically processed into avalue that represents the analyte level and that is readily suitable fordisplay to the user, and this can occur in sensor control device 102,reader device 120, or computer system 170. This and any otherinformation derived from the raw data can be displayed in any of themanners described above (with respect to display 122) on any displayresiding on any of sensor control device 102, reader device 120, orcomputer system 170. The information may be utilized by the user todetermine any necessary corrective actions to ensure the analyte levelremains within an acceptable and/or clinically safe range.

As discussed above, reader device 120 can be a mobile communicationdevice such as, for example, a Wi-Fi or internet enabled smartphone,tablet, or personal digital assistant (PDA). Examples of smartphones caninclude, but are not limited to, those phones based on a WINDOWSoperating system, ANDROID operating system, IPHONE operating system,PALM WEBOS, BLACKBERRY operating system, or SYMBIAN operating system,with network connectivity for data communication over the internet or alocal area network (LAN).

Reader device 120 can also be configured as a mobile smart wearableelectronics assembly, such as an optical assembly that is worn over oradjacent to the user's eye (e.g., a smart glass or smart glasses, suchas GOOGLE GLASSES). This optical assembly can have a transparent displaythat displays information about the user's analyte level (as describedherein) to the user while at the same time allowing the user to seethrough the display such that the user's overall vision is minimallyobstructed. The optical assembly may be capable of wirelesscommunications similar to a smartphone. Other examples of wearableelectronics include devices that are worn around or in the proximity ofthe user's wrist (e.g., a watch, etc.), neck (e.g., a necklace, etc.),head (e.g., a headband, hat, etc.), chest, or the like.

FIG. 6B is a block diagram of an example embodiment of a reader device120 in the form of a smartphone. Here, reader device 120 includes aninput component 121, display 122, and processing hardware 206, which caninclude one or more processors, microprocessors, controllers, and/ormicrocontrollers, each of which can be a discrete chip or distributedamongst (and a portion of) a number of different chips. Processinghardware 206 can include a communications processor 202 having on-boardmemory 203 and an applications processor 204 having on-board memory 205.Additional processors can and will likely be present. Reader device 120further includes an RF transceiver 208 coupled with an RF antenna 209, amemory 210, multi-functional circuitry 212 with one or more associatedantennas 214, a power supply 216, and power management circuitry 218.FIG. 6B is an abbreviated representation of the internal components of asmartphone, and other hardware and functionality (e.g., codecs, drivers,glue logic, etc.) can of course be included.

Communications processor 202 can interface with RF transceiver 208 andperform analog-to-digital conversions, encoding and decoding, digitalsignal processing and other functions that facilitate the conversion ofvoice, video, and data signals into a format (e.g., in-phase andquadrature) suitable for provision to RF transceiver 208, which can thentransmit the signals wirelessly. Communications processor 202 can alsointerface with RF transceiver 208 to perform the reverse functionsnecessary to receive a wireless transmission and convert it into digitaldata, voice, and video.

Applications processor 204 can be adapted to execute the operatingsystem and any software applications that reside on reader device 120,process video and graphics, and perform those other functions notrelated to the processing of communications transmitted and receivedover RF antenna 209. Any number of applications can be running on readerdevice 120 at any one time, and will typically include one or moreapplications that are related to a diabetes monitoring regime, inaddition to the other commonly used applications that are unrelated tosuch a regime, e.g., email, calendar, weather, etc.

Memory 210 can be shared by one or more the various functional unitspresent within reader device 120, or can be distributed amongst two ormore of them (e.g., as separate memories present within differentchips). Memory 210 can also be a separate chip of its own. Memory 210 isnon-transitory, and can be volatile (e.g., RAM, etc.) and/ornon-volatile memory (e.g., ROM, flash memory, F-RAM, etc.).

Multi-functional circuitry 212 can be implemented as one or more chipsand/or components, including communication circuitry, that perform otherfunctions such as local wireless communications (e.g., Wi-Fi, Bluetooth,Bluetooth Low Energy) and determining the geographic position of readerdevice 120 (e.g., global positioning system (GPS) hardware). One or moreother antennas 214 are associated with the functional circuitry 212 asneeded.

Power supply 216 can include one or more batteries, which can berechargeable or single-use disposable batteries. Power managementcircuitry 218 can regulate battery charging and power supply monitoring,boost power, perform DC conversions, and the like. As mentioned, readerdevice 120 may also include one or more data communication ports such asUSB port (or connector) or RS-232 port (or any other wired communicationports) for data communication with a remote terminal 170, or sensorcontrol device 102, to name a few. A network syncing clock 219 is alsopresent that can provide the system time and include, for example, an RCor crystal oscillator and associated clock buffers and distributioncircuitry.

FIG. 6C is a block schematic diagram depicting an example embodiment ofsensor control device 102 having analyte sensor 104 and sensorelectronics 250 (including analyte monitoring circuitry). Although anynumber of chips can be used, here the majority of the sensor electronics250 are incorporated on a single semiconductor chip 251 that can be,e.g., a custom application specific integrated circuit (ASIC). Shownwithin ASIC 201 are several high-level functional units, including ananalog front end (AFE) 252, power management circuitry 254, processor256, and communication circuitry 258 (which can be implemented as atransmitter, receiver, transceiver, passive circuit, or otherwiseaccording to the communication protocol). In this embodiment, both AFE252 and processor 256 are used as analyte monitoring circuitry, but inother embodiments either circuit can perform the analyte monitoringfunction. Processor 256 can include one or more processors,microprocessors, controllers, and/or microcontrollers.

A non-transitory memory 253 is also included within ASIC 251 and can beshared by the various functional units present within ASIC 251, or canbe distributed amongst two or more of them. Memory 253 can be volatileand/or non-volatile memory. In this embodiment, ASIC 251 is coupled withpower source 260, which can be a coin cell battery, or the like. AFE 252interfaces with in vivo analyte sensor 104 and receives measurement datatherefrom and outputs the data to processor 256 in digital form, whichin turn processes the data to arrive at the end-result analyte discreteand trend values, etc. This data can then be provided to communicationcircuitry 258 for sending, by way of antenna 261, to reader device 120(not shown) where further processing can be performed by, e.g., thesensor interface application.

A clock 255 is also present that can be, for example, an RC or crystaloscillator. Clock 255 can be a monotonic clock that moves forward atconstant rate (subject to environmental drift) and continues for theentire life of the sensor without interruption. In some embodiments,sensor control device 102 can keep time by generating an interrupt aftera predetermined number of seconds (e.g., every second, or every minuteetc.), where the interrupt increments a software or hardware counter.The counter value reflects the number of predetermined time spans thathave passed since the sensor was activated. For example, if theinterrupt is generated every minute, then the counter value reflects thenumber of minutes that have passed since activation of the sensorcontrol device 102.

It should be noted that the functional components of ASIC 251 can alsobe distributed amongst two or more discrete semiconductor chips.

Sensor Configurations

Analytes that may be monitored with system 100 include, but are notlimited to, acetyl choline, amylase, bilirubin, cholesterol, chorionicgonadotropin, glycosylated hemoglobin (HbAlc), creatine kinase (e.g.,CK-MB), creatine, creatinine, DNA, fructosamine, glucose, glucosederivatives, glutamine, growth hormones, hormones, ketones, ketonebodies, lactate, oxygen, peroxide, prostate-specific antigen,prothrombin, RNA, thyroid stimulating hormone, and troponin. Theconcentration of drugs, such as, for example, antibiotics (e.g.,gentamicin, vancomycin, and the like), digitoxin, digoxin, drugs ofabuse, theophylline, and warfarin, may also be monitored. In embodimentsthat monitor more than one analyte, the analytes may be monitored at thesame or different times with a single sensor or with a plurality ofsensors which may use the same electronics (e.g., simultaneously) orwith different electronics of sensor control device 102.

Analyte sensor 104 may include an analyte-responsive enzyme to provide asensing element. Some analytes, such as oxygen, can be directlyelectrooxidized or electroreduced on sensor 104, and more specificallyat least on a working electrode (not shown) of a sensor 104. Otheranalytes, such as glucose and lactate, require the presence of at leastone electron transfer agent and/or at least one catalyst to facilitatethe electrooxidation or electroreduction of the analyte. Catalysts mayalso be used for those analytes, such as oxygen, that can be directlyelectrooxidized or electroreduced on the working electrode. For theseanalytes, each working electrode includes a sensing element proximate toor on a surface of a working electrode. In many embodiments, a sensingelement is formed near or on only a small portion of at least a workingelectrode.

Each sensing element includes one or more components constructed tofacilitate the electrochemical oxidation or reduction of the analyte.The sensing element may include, for example, a catalyst to catalyze areaction of the analyte and produce a response at the working electrode,an electron transfer agent to transfer electrons between the analyte andthe working electrode (or other component), or both.

Electron transfer agents that may be employed are electroreducible andelectrooxidizable ions or molecules having redox potentials that are afew hundred millivolts above or below the redox potential of thestandard calomel electrode (SCE). The electron transfer agent may beorganic, organometallic, or inorganic. Examples of organic redox speciesare quinones and species that in their oxidized state have quinoidstructures, such as Nile blue and indophenol. Examples of organometallicredox species are metallocenes including ferrocene. Examples ofinorganic redox species are hexacyanoferrate (III), ruthenium hexamine,etc. Additional examples include those described in U.S. Pat. Nos.6,736,957, 7,501,053 and 7,754,093, the disclosures of each of which areincorporated herein by reference in their entirety.

In certain embodiments, electron transfer agents have structures orcharges which prevent or substantially reduce the diffusional loss ofthe electron transfer agent during the period of time that the sample isbeing analyzed. For example, electron transfer agents include but arenot limited to a redox species, e.g., bound to a polymer which can inturn be disposed on or near the working electrode. The bond between theredox species and the polymer may be covalent, coordinative, or ionic.Although any organic, organometallic or inorganic redox species may bebound to a polymer and used as an electron transfer agent, in certainembodiments the redox species is a transition metal compound or complex,e.g., osmium, ruthenium, iron, and cobalt compounds or complexes. Itwill be recognized that many redox species described for use with apolymeric component may also be used, without a polymeric component.

Embodiments of polymeric electron transfer agents may contain a redoxspecies covalently bound in a polymeric composition. An example of thistype of mediator is poly(vinylferrocene). Another type of electrontransfer agent contains an ionically-bound redox species. This type ofmediator may include a charged polymer coupled to an oppositely chargedredox species. Examples of this type of mediator include a negativelycharged polymer coupled to a positively charged redox species such as anosmium or ruthenium polypyridyl cation.

Another example of an ionically-bound mediator is a positively chargedpolymer including quaternized poly (4-vinyl pyridine) or poly(1-vinylimidazole) coupled to a negatively charged redox species such asferricyanide or ferrocyanide. In other embodiments, electron transferagents include a redox species coordinatively bound to a polymer. Forexample, the mediator may be formed by coordination of an osmium orcobalt 2,2′-bipyridyl complex to poly(1-vinyl imidazole) or poly(4-vinylpyridine).

Suitable electron transfer agents are osmium transition metal complexeswith one or more ligands, each ligand having a nitrogen-containingheterocycle such as 2,2′-bipyridine, 1,10-phenanthroline, 1-methyl,2-pyridyl biimidazole, or derivatives thereof. The electron transferagents may also have one or more ligands covalently bound in a polymer,each ligand having at least one nitrogen-containing heterocycle, such aspyridine, imidazole, or derivatives thereof. One example of an electrontransfer agent includes (a) a polymer or copolymer having pyridine orimidazole functional groups and (b) osmium cations complexed with twoligands, each ligand containing 2,2′-bipyridine, 1,10-phenanthroline, orderivatives thereof, the two ligands not necessarily being the same.Some derivatives of 2,2′-bipyridine for complexation with the osmiumcation include but are not limited to 4,4′-dimethyl-2,2′-bipyridine andmono-, di-, and polyalkoxy-2,2′-bipyridines, including4,4′-dimethoxy-2,2′-bipyridine. Derivatives of 1,10-phenanthroline forcomplexation with the osmium cation include but are not limited to4,7-dimethyl-1,10-phenanthroline and mono, di-, andpolyalkoxy-1,10-phenanthrolines, such as4,7-dimethoxy-1,10-phenanthroline. Polymers for complexation with theosmium cation include but are not limited to polymers and copolymers ofpoly(1-vinyl imidazole) (referred to as “PVI”) and poly(4-vinylpyridine) (referred to as “PVP”). Suitable copolymer substituents ofpoly(1-vinyl imidazole) include acrylonitrile, acrylamide, andsubstituted or quaternized N-vinyl imidazole, e.g., electron transferagents with osmium complexed to a polymer or copolymer of poly(l-vinylimidazole).

Embodiments may employ electron transfer agents having a redox potentialranging from about −200 mV to about +200 mV versus the standard calomelelectrode (SCE). The sensing elements may also include a catalyst whichis capable of catalyzing a reaction of the analyte. The catalyst mayalso, in some embodiments, act as an electron transfer agent. Oneexample of a suitable catalyst is an enzyme which catalyzes a reactionof the analyte. For example, a catalyst, including a glucose oxidase,glucose dehydrogenase (e.g., pyrroloquinoline quinone (PQQ), dependentglucose dehydrogenase, flavine adenine dinucleotide (FAD) dependentglucose dehydrogenase, or nicotinamide adenine dinucleotide (NAD)dependent glucose dehydrogenase), may be used when the analyte ofinterest is glucose. A lactate oxidase or lactate dehydrogenase may beused when the analyte of interest is lactate. Laccase may be used whenthe analyte of interest is oxygen or when oxygen is generated orconsumed in response to a reaction of the analyte.

In certain embodiments, a catalyst may be attached to a polymer, crosslinking the catalyst with another electron transfer agent, which, asdescribed above, may be polymeric. A second catalyst may also be used incertain embodiments. This second catalyst may be used to catalyze areaction of a product compound resulting from the catalyzed reaction ofthe analyte. The second catalyst may operate with an electron transferagent to electrolyze the product compound to generate a signal at theworking electrode. Alternatively, a second catalyst may be provided inan interferent-eliminating layer to catalyze reactions that removeinterferents.

In certain embodiments, the sensor works at a low oxidizing potential,e.g., a potential of about +40 mV vs. Ag/AgCl. These sensing elementsuse, for example, an osmium (Os)-based mediator constructed for lowpotential operation. Accordingly, in certain embodiments the sensingelements are redox active components that include: (1) osmium-basedmediator molecules that include (bidente) ligands, and (2) glucoseoxidase enzyme molecules. These two constituents are combined togetherin the sensing elements of the sensor.

A number of embodiments of sensor configurations that may be used insystem 100 are described in Int'l Publication No. WO 2012/174538, titled“Connectors for Making Connections between Analyte Sensors and OtherDevices,” and also in U.S. Pat. No. 8,435,682, titled “Biological FuelCell and Methods,” both of which are incorporated by reference herein intheir entirety for all purposes. Particular attention is drawn toparagraphs 121-145 of the '528 Publication, several of which arereproduced herein.

The subject matter described herein was done so primarily in the contextof in vivo analyte monitoring systems. In vivo systems can bedifferentiated from “in vitro” systems that contact a biological sampleoutside of the body (or rather “ex vivo”) and that typically include ameter device that has a port for receiving an analyte test stripcarrying the biological sample of the user, which can be analyzed todetermine the user's blood sugar level. Many in vitro systems require a“finger stick” to obtain the biological sample. In vivo analytemonitoring systems, however, can operate without the need for fingerstick calibration.

The embodiments described herein can be used with in vivo analytemonitoring systems that incorporate in vitro capability, as well haspurely in vitro or ex vivo analyte monitoring systems. Furthermore, theembodiments described herein can be used in systems, devices, andmethods outside of the analyte monitoring field, either in other medicaldevice fields, or in any other field where the subject matter describedherein can reap benefit.

All features, elements, components, functions, and steps described withrespect to any embodiment provided herein are intended to be freelycombinable and substitutable with those from any other embodiment. If acertain feature, element, component, function, or step is described withrespect to only one embodiment, then it should be understood that thatfeature, element, component, function, or step can be used with everyother embodiment described herein unless explicitly stated otherwise.This paragraph therefore serves as antecedent basis and written supportfor the introduction of claims, at any time, that combine features,elements, components, functions, and steps from different embodiments,or that substitute features, elements, components, functions, and stepsfrom one embodiment with those of another, even if the followingdescription does not explicitly state, in a particular instance, thatsuch combinations or substitutions are possible. Express recitation ofevery possible combination and substitution is overly burdensome,especially given that the permissibility of each and every suchcombination and substitution will be readily recognized by those ofordinary skill in the art upon reading this description.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise.

While the embodiments are susceptible to various modifications andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. It should be understood,however, that these embodiments are not to be limited to the particularform disclosed, but to the contrary, these embodiments are to cover allmodifications, equivalents, and alternatives falling within the spiritof the disclosure. Furthermore, any features, functions, steps, orelements of the embodiments may be recited in or added to the claims, aswell as negative limitations that define the inventive scope of theclaims by features, functions, steps, or elements that are not withinthat scope.

What is claimed is:
 1. A method for in vivo glucose monitoring of asubject's glucose levels, the method comprising: powering on a firstsensor control device disposed on skin of the subject, the first sensorcontrol device comprising a first subcutaneous glucose sensor, a firstprocessor, and a first wireless communication circuitry configured towirelessly communicate with a reader device, wherein a first portion ofthe first subcutaneous glucose sensor is configured to be positionedunder the skin and in contact with interstitial fluid of the subject,and wherein a second portion of the first subcutaneous glucose sensor iselectrically coupled with in vivo glucose monitoring circuitry of thefirst sensor control device; entering a warm-up period of the firstsensor control device; displaying, by the reader device, a first dataindicative of the subject's glucose levels from the first sensor controldevice after exiting the warm-up period of the first sensor controldevice; powering on a second sensor control device disposed on the skinof the subject while the first sensor control device is also disposed onthe skin, the second sensor control device comprising a secondsubcutaneous glucose sensor, a second processor, and a second wirelesscommunication circuitry configured to wireless communicate with thereader device, wherein a first portion of the second subcutaneousglucose sensor is configured to be positioned under the skin and incontact with the interstitial fluid of the subject, and wherein a secondportion of the second subcutaneous glucose sensor is electricallycoupled with in vivo glucose monitoring circuitry of the second sensorcontrol device; entering a warm-up period of the second sensor controldevice; and displaying, by the reader device, a second data indicativeof the subject's glucose levels from the first sensor control deviceduring the warm-up period of the second sensor control device.
 2. Themethod of claim 1, further comprising: displaying, by the reader device,a third data indicative of the subject's glucose levels from the secondsensor control device after exiting the warm-up period of the secondsensor control device.
 3. The method of claim 2, further comprisingdisplaying, by the reader device, at least a portion of the second dataindicative of the subject's glucose levels and at least a portion of thethird data indicative of the subject's glucose levels at the same time.4. The method of claim 2, further comprising: receiving, by the readerdevice, a first sensor identifier associated with the first sensorcontrol device.
 5. The method of claim 4, further comprising: receiving,by the reader device, a second sensor identifier associated with thesecond sensor control device, wherein the second sensor identifier isunique from the first sensor identifier.
 6. The method of claim 5,wherein the first sensor identifier is communicated to the reader devicealong with the first data indicative of the subject's glucose levels andthe second data indicative of the subject's glucose levels, and whereinthe second sensor identifier is communicated to the reader device alongwith the third data indicative of the subject's glucose levels.
 7. Themethod of claim 1, wherein the second sensor control device isconfigured to be applied on the skin of the subject before an operatinglife of the first sensor control device has expired.
 8. The method ofclaim 7, further comprising: terminating operation of the first sensorcontrol device after the operating life of the first sensor controldevice has expired.
 9. The method of claim 1, further comprising:terminating operation of the first sensor control device after exitingthe warm-up period of the second sensor control device.
 10. The methodof claim 1, further comprising: pairing the reader device with the firstsensor control device.
 11. The method of claim 10, further comprising:pairing the reader device with the second sensor control device.
 12. Themethod of claim 11, wherein the second sensor control device is pairedwith the reader device after the first sensor control device is pairedwith the reader device.
 13. The method of claim 1, wherein the readerdevice comprises a memory coupled with one or more processors of thereader device, the memory storing software that, when executed by theone or more processors of the reader device, causes the one or moreprocessors of the reader device to identify the first sensor controldevice as a primary sensor control device while receiving the first dataindicative of the subject's glucose levels.
 14. The method of claim 13,wherein the software stored in the memory of the reader device, whenexecuted by the one or more processors of the reader device, furthercauses the one or more processors of the reader device to identify thefirst sensor control device as the primary sensor control device whilereceiving the second data indicative of the subject's glucose levels.15. The method of claim 14, wherein the software stored in the memory ofthe reader device, when executed by the one or more processors of thereader device, further causes the one or more processors of the readerdevice to identify the second sensor control device as the primarysensor control device after exiting the warm-up period of the secondsensor control device.
 16. The method of claim 1, wherein the readerdevice is configured to display a list of active and inactive sensorcontrol devices.
 17. The method of claim 1, wherein the reader devicecomprises a memory coupled with one or more processors of the readerdevice, the memory storing software that, when executed by the one ormore processors of the reader device, causes the one or more processorsof the reader device to display an activation time of the first sensorcontrol device.
 18. The method of claim 17, wherein the software storedin memory, when executed by the one or more processors of the readerdevice, further causes the one or more processors of the reader deviceto display an expiration time of the first sensor control device. 19.The method of claim 1, wherein the reader device is a smartphone.
 20. Anin vivo glucose monitoring system, comprising: a reader device; a firstsensor control device configured to be powered on and disposed on skinof a subject, the first sensor control device comprising a firstsubcutaneous glucose sensor, a first processor, and a first wirelesscommunication circuitry, wherein a first portion of the firstsubcutaneous glucose sensor is configured to be positioned under theskin and in contact with interstitial fluid of the subject, and whereina second portion of the first subcutaneous glucose sensor iselectrically coupled with in vivo glucose monitoring circuitry of thefirst sensor control device; and a second sensor control deviceconfigured to be powered on and disposed on the skin of the subjectwhile the first sensor control device is also disposed on the skin, thesecond sensor control device comprising a second glucose sensor, asecond processors, and a second wireless communication circuitry,wherein a first portion of the second sensor control device isconfigured to be positioned under the skin and in contact with theinterstitial fluid of the subject, and wherein a second portion of thesecond subcutaneous glucose sensor is electrically coupled with in vivoglucose monitoring circuitry of the second sensor control device,wherein the first sensor control device is further configured to enter awarm-up period of the first sensor control device, and wherein thereader device is configured to display a first data indicative of thesubject's glucose levels from the first sensor control device afterexiting the warm-up period of the first sensor control device, andwherein the second sensor control device is further configured to entera warm-up period of the second sensor control device, and wherein thereader device is further configured to display a second data indicativeof the subject's glucose levels from the first sensor control deviceduring the warm-up period of the second sensor control device.
 21. Thein vivo glucose monitoring system of claim 20, wherein the reader deviceis further configured to display a third data indicative of thesubject's glucose levels from the second sensor control device afterexiting the warm-up period of the second sensor control device.
 22. Thein vivo glucose monitoring system of claim 21, wherein the first sensorcontrol device is further configured to communicate a first sensoridentifier to the reader device along with the first data indicative ofthe subject's glucose levels and the second data indicative of thesubject's glucose levels, and wherein the second sensor control deviceis further configured to communicate a second sensor identifier to thereader device along with the third data indicative of the subject'sglucose levels.
 23. The in vivo glucose monitoring system of claim 21,wherein the reader device is a smartphone.
 24. The in vivo glucosemonitoring system of claim 20, wherein the second sensor control deviceis configured to be applied on the skin of the subject before anoperating life of the first sensor control device has expired.
 25. Thein vivo glucose monitoring system of claim 24, wherein operation of thefirst sensor control device is configured to be terminated after theoperating life of the first sensor control device has expired.
 26. Thein vivo glucose monitoring system of claim 20, wherein operation thefirst sensor control device is configured to be terminated after exitingthe warm-up period of the second sensor control device.
 27. The in vivoglucose monitoring system of claim 20, wherein the reader device isconfigured to display a list of active and inactive sensor controldevices.
 28. The in vivo glucose monitoring system of claim 20, whereinthe reader device comprises a memory coupled with one or more processorsof the reader device, the memory storing software that, when executed bythe one or more processors of the reader device, causes the one or moreprocessors of the reader device to display an activation time of thefirst sensor control device.
 29. The in vivo glucose monitoring systemof claim 28, wherein the software, stored in memory, when executed bythe one or more processors of the reader device, further causes the oneor more processors of the reader device to display an expiration time ofthe first sensor control device.